1. Technical Field
The present invention relates to a printing apparatus, a printing apparatus control program, and a printing apparatus control method, which are used for printing equipment such as a facsimile machine, a copier, and Office Automation (OA) appliances, a printing apparatus, a printing apparatus control program, a printing apparatus control method, a printing data creating apparatus, a printing data creating program, and a printing data creating method particularly to so-called ink jet printing processing in which fine particles of multiple colors of liquid ink are discharged onto printing paper (recording material) to form predetermined letters and images.
2. Related Art
Hereinafter, a printing apparatus, particularly a printer that adopts the ink jet printing method (hereinafter, it is called ‘an ink jet printer’) will be described.
Generally, since the ink jet printer easily provides inexpensive, high quality color prints, it becomes widespread in offices as well as general users with the wide use of personal computers and digital cameras.
Typically, the ink jet printer like this produces desired prints in which a movable body called a carriage having an ink cartridge and a print head in one piece discharges (ejects) liquid ink particles in dots from a nozzle of the print head while reciprocating over a printing medium (for example, printing paper) in the direction vertical to the paper feed direction and predetermined letters and images onto the medium are drawn. Then, four colors of ink cartridges including black (black, yellow, magenta, and cyan) and print heads for each color are provided in this carriage to facilitate monochrome printing as well as full color printing combining each color (furthermore, such a ink jet printer is also commercially available that is provided with six and seven colors, or eight colors such as light cyan and light magenta added to these colors).
Moreover, in the ink jet printer of this type that printing is done while the print head over the carriage reciprocates in the direction vertical to the paper feed direction, the print head needs to reciprocate ten to a hundred times or more in order to print an entire page beautifully. Thus, as compared with a printing apparatus in other methods such as a laser printer using electrophotographic technology including a copier, it has a disadvantage that it takes longer to print.
On the other hand, in an ink jet printer of the type that a long print head having the same width (or longer) as that of printing paper is disposed without using any carriage, the print head does not need to move in the width direction of printing paper, and printing is done in a so-called single scan (a single path). Therefore, high speed printing is feasible similar to the laser printer. Furthermore, since a carriage that mounts the print head thereon and a drive system that moves the carriage are unnecessary, this printer has advantages that a printer housing can be reduced in size and weight, and noise reduction properties can be improved significantly. Moreover, the ink jet printer by the former method is generally called a ‘multipath type printer’, and the ink jet printer by the latter method is generally called a ‘line scan head type printer’ or ‘serial printer’.
In the meantime, since the print head essential for the ink jet printer like these is formed in which fine nozzles each having a diameter of about 10 to 70 μm are arranged in a row spaced at a predetermined distance or in multiple rows in the printing direction, a so-called ‘curved flight phenomenon’ sometimes occurs that fabrication error causes a part of nozzles to be tilted in the ink discharge direction thereof, or that the position of a nozzle is placed at the position shifted from an ideal position and then the position of dot ejected by that nozzle is shifted from an ideal position. Furthermore, because of the variations in the property of the nozzle, for the nozzle with greater variations, there are some nozzles that an ink amount is greatly larger or smaller than an ideal amount.
Consequently, a print failure known as a so-called ‘banding (streaks) phenomenon’ is generated in the portion printed with the defective nozzle, and print quality is sometimes seriously degraded. More specifically, when the ‘curved flight’ phenomenon occurs, the distance between dots discharged from the adjacent nozzles becomes uneven, ‘white streaks (when printing paper is white)’ are generated in the portion where the distance between adjacent dots is larger than in normal printing, and ‘thick streaks’ are generated in the portion where the distance between adjacent dots is shorter than in normal printing. Furthermore, also when the value of the ink amount is deviated from an ideal value, thick streaks are generated in the portion relating to the nozzle with a greater ink amount, and white streaks are generated in the portion relating to the nozzle with a smaller ink amount.
Particularly, such the banding phenomenon tends to occur more noticeably in the ‘line scan head type printer’ that the print head or a medium for use in printing is fixed (single path printing) than in the ‘multipath type printer’ (serial printer) described above (in the multipath type printer, there is a technique to make banding less noticeable with making use of reciprocating the print head many times).
Therefore, in order to prevent a kind of printed failure like this ‘banding phenomenon’, studies and development are done in so-called hardware including improvements in fabrication techniques and in designs of the print head, but it is difficult to provide a print head that never generates the ‘banding phenomenon’ in view of fabrication cost and available hardware technology.
Then, under the current circumstances, in addition to the improvements in hardware, a technique is also used to reduce the ‘banding phenomenon’ using so-called software schemes such as print control shown below.
For example, in Patent Reference 1 (JP-A-2002-19101) and Patent Reference 2 (JP-A-2003-136702) shown below, in order to cope with nozzle variations and no ink discharge, settings are done to make banding and variations less noticeable in such ways that head variations are handled by using a shading compensation technique for portions with thin concentrations, and that other colors are used for substitutes for portions with thick concentrations (for example, when printing is done in black, cyan, magenta, etc., are substituted).
Moreover, in Patent Reference 3 (JP-A-2003-63043) shown below, a scheme is adopted for a solid image (that is, it is an image having a relatively great area with respect to a line image, which is covered with ink densely, but is sometimes not covered entirely because of edge effect), in which the discharge amount of nozzles adjacent to neighboring pixels of a misfired nozzle is increased to generate a solid image by all the nozzles.
Furthermore, in Patent Reference 4 (JP-A-5-30361) shown below, an amount of variations in each of nozzles is fed back to error spread and processed, and variations in the discharge amount of ink discharged from the nozzles are smoothed out to prevent the banding phenomenon.
Moreover, in Patent Reference 5 (JP-A-2004-58284) shown below, when there is a nozzle (N) that abnormality occurs in an ink discharge state, record data corresponding to that abnormal nozzle (N) is added to record data corresponding to neighboring nozzles (N−1) and (N+1) located near the abnormal nozzle (N), and record data corresponding to the abnormal nozzle (N) is corrected to prevent the banding phenomenon.
However, for portions with thick concentrations, in the schemes that information about the no discharge nozzle is distributed in right and left to prevent the ‘white streak phenomenon’ in the traditional techniques as Patent Reference 1 and Patent Reference 2, when it is adopted to ‘the curved flight phenomenon’ described above, it has a problem that banding still remains in portions with thick concentrations.
Moreover, in the scheme as traditional technique of the Patent Reference 3, no problem occurs when prints are solid images, but the scheme cannot be used for halftone prints. Besides, the scheme that buries fine lines with other colors does not cause any problem for slight use, but for an image where different colors are created continuously, a problem remains that the hue of the image is partially changed similar to the former scheme.
Furthermore, in the scheme as the traditional technique of the Patent Reference 4, for the problem that dot forming descriptions are shifted, there is a problem that the process of proper feedback is complicated for difficult solution.
Moreover, in the scheme as the traditional technique of the Patent Reference 5, when dots have the γ property in creating dots in different size by surrounding nozzles after binarization, a problem occurs that the area ratio gray scale in that portion is likely to be deformed.